1. Technical Field
An embodiment of the present disclosure relates to a photoelectric conversion element evaluation apparatus.
2. Description of the Related Art
For characteristics evaluation of a photoelectric conversion element (such as a solar cell), the current-voltage characteristic of the solar cell is measured to calculate its maximum output power (Pmax), for example. In addition, conversion efficiency (PCE) is calculated to provide a determination parameter. The conversion efficiency is computed by dividing the maximum output power by the irradiation output power of simulated sunlight and the area of the solar cell.
FIG. 11 is a block diagram of an example of a known solar cell evaluation apparatus. A solar cell 101 as the object of measurement is irradiated with simulated sunlight from a simulated sunlight source 102. Between the electrodes of the solar cell 101, a load 103 is connected in series with an ammeter 104. Between the electrodes of the solar cell 101, a voltmeter 105 is connected in parallel with the load 103.
The maximum output power Pmax and the conversion efficiency PCE of the solar cell 101 are calculated by determining a current-voltage characteristic curve as shown in FIG. 12. The current-voltage characteristic curve is determined as follows, for example. The solar cell 101 is irradiated with simulated sunlight from the simulated sunlight source 102. In this state, current is measured by the ammeter 104 and voltage is measured by the voltmeter 105 while the load 103 connected between the electrodes of the solar cell 101 is varied.
In FIG. 12, ΔIoc is the amount of current decrease from the current in an open-circuit state. ΔVoc is the amount of voltage decrease from the voltage in the open-circuit state. A parallel resistance component Rsh in the solar cell 101 is determined according to the following expression:Rsh=−ΔVoc/ΔIoc 
ΔIsc is the amount of current decrease from the current in a nearly short-circuited state. ΔVsc is the amount of voltage decrease from the voltage in the nearly short-circuited state. A series resistance component Rs in the solar cell 101 is determined according to the following expression:Rs=−ΔVsc/ΔIsc 
The conversion efficiency PCE can be determined according to the following expression:PCE=Pmax/(E·A)where Pmax is the maximum output power, E is the irradiation power of the simulated sunlight with which the solar cell 101 is irradiated from the simulated sunlight source 102, and A is the area of the solar cell 101.
The current at the time of the maximum output power Pmax is a maximum output current Imax, and the voltage at the time of the maximum output power Pmax is a maximum output voltage Vmax.
JP-A-8-64652 describes an inspection method for evaluating the light emission output and response rate of a product while in the state of an epitaxial wafer.